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Preparation and characterization of monolithic alumina aerogels

“…It is apparent that gelation time increases rapidly with increasing concentration of nitric acid. It shrinks by about 16% and loses its coloration after heat treatment at 600°C for 2 h. It shrinks more (≈9%) and becomes white and opaque but no cracking occurs after heat treatment at 800°C for 2 h. These shrinkages after heat treatment are similar to those of alumina aerogels prepared using ethyl acetoacetate as complexing agents [6] and smaller than those of alumina aerogels prepared from AlCl 3 ·6H 2 O and Al(NO 3 ) 3 ·9H 2 O [8]. It shows better thermal stability than alumina aerogels derived from hydrated aluminum salts.…”

“…[5][6][7][8][9][10][11][12][13][14][15] Preparation of alumina aerogel monoliths from aluminum alkoxide was typically difficult because of the complex chemical pathways leading to gelation, high reactivity of the aluminum alkoxide and the susceptibility to cracking during drying [5]. Complex solvent mixtures or the addition of chelating agents were usually required to control the hydrolysis and condensation rates of aluminum alkoxide.…”

“…Complex solvent mixtures or the addition of chelating agents were usually required to control the hydrolysis and condensation rates of aluminum alkoxide. Up to now, relatively few papers described the formation of pure monolithic alumina aerogels from alkoxide [5][6][7].…”

Supercritical preparation of hexagonal γ-alumina nanosheets and its electrocatalytic properties

“…One efficient way to minimize stress is the supercritical fluid drying [21,22]. In a typical sol-gel approach, aluminum alkoxides [23][24][25], such as aluminum isopropoxide or aluminum sec-butoxide [26][27][28][29], are usually sources of alumina aerogels [30][31][32][33]. However, these aluminum alkoxides are very reactive, which makes sol-gel formation hard to control.…”

Preparation and characterization of aerogels derived from Al(OH)3 and CrO3

“…Synthesis and drying procedures leading to Al 2 O 3 and Cr 2 O 3 aerogels, as either primary or binary oxides, have been available for some time. Alumina aerogels are most commonly prepared by a standard sol-gel approach through the hydrolysis and condensation of a sterically hindered aluminum alkoxide, such as an s-butoxide, or an acetylacetonate [8][9][10][11]. However, there has been one recent report of the preparation of alumina aerogels by the reaction of aluminum nitrate with propylene oxide [12].…”